The present invention relates to the field of metal refining, and in particular relates to a method and apparatus for distilling a metal which it is desired to recover from a mixture of said metal and another element which has a relatively lower vapor pressure than said metal at a relatively high temperature.
The present patent application has been at least partially prepared from material which has been included in Japanese Patent Application No. Sho 59-253417 (1984), which was invented by the same inventors as the present patent application, and the present patent application hereby incorporates the text of that Japanese Patent Application and the claims in the drawings thereof into this specification by reference; a copy is appended to this specification.
There exists in the art a reasonably effective process for separating such a metal as magnesium or zinc from a molten alloy consisting of a magnesium or zinc component, which has a relatively high vapor pressure at a relatively high temperature, and a second element such as lead or aluminum, which has a relatively low vapor pressure at said relatively high temperature. The technique takes advantage of the difference in vapor pressure of the components of the molten metal alloy by distilling said alloy in a vacuum. This technique is the so called "Vacuum Distilling Method", or alternatively the "Volatilization Method". (See "Compendium of Metals", revised edition, published by Maruzen, pages 324-330). The distilling apparatus required to execute this method normally comprises: a vaporization container consisting of an internal sealed chamber with a molten alloy introduction port and a separate vapor removal port; a condenser consisting of an internal sealed chamber with a vapor introduction port and a separate discharge port; a connecting conduit linking the vapor removal port of the vaporization container to the vapor introduction port of the condenser; and a means for heating the inside of the vaporization container to a certain fixed temperature; said means heating the molten alloy introduced to the vaporization container and causing said molten alloy to vaporize and, further, causing the metal vapor thus formed to travel to the condenser through the connecting conduit linking the evaporation container and said condenser; said condenser, in addition to the above stated features, comprising an internal vessel which, when cooled, causes the metal vapor introduced thereto to condense.
However, in a process and apparatus of the above described kind, when the viscosity of the metal desired to be recovered is low or when the difference between the vapor pressures of the respective components of the metal alloy to be treated is not sufficiently great, the process must be executed numerous times in order to achieve a high degree of purity for the metal desired to be recovered. An alternative to this prior art type of method is the New Jersey Process (reference should be made to the publication "Non-ferrous Metal Refining", The Metals Academic Society, p. 129) for refining rough zinc, wherein a distilling tower of fifty stories or more is necessary, the expenditure of energy is great, the distilling process itself requires excessive time, and the required apparatus is of large size. With either of the two above mentioned processes, it is impossible to distil metals cheaply and efficiently.